In this proposal studies are outlined to investigate the functional relations between handedness, hand posture in writing, cerebral asymmetry, and characteristics of the motor control pathways to the hands. Approximately 7 percent of the population has the linguistically specialized hemisphere iipsilateral to the dominant hand and previous research revealed that these individuals adopt an inverted hand posture during writing. There is little understanding of the mechanisms of hand control in such people, and all hypotheses thus far suggested are, to varying degrees, inconsistent with observations. The proposed investigation will allow assessment of the validity of the different hypotheses and will provide information on the relationships among hemispheric specialization, manual pathways, and the precisi n of manual movement. Individual differences in these relationships imply variation in cognitive laterality patterns and in neurobehavioral associations, and an understanding of their underlying substrates is felt to be a first and critical step in elucidating how the neurology of higher cognitive functions governs psychological organization.